The development and validation of a radiographic grading system for the hip in ankylosing spondylitis: the Bath Ankylosing Spondylitis Radiology Hip Index

Objective. To develop a simple bur reproducible radiological scoring system for the hip in ankylosing spondylitis (AS). Methods. A consensus approach was used to develop a grading system whereby hip radiographs of 470 patients with AS were scored from 0 to 3 (normal, su spicious, mild, moderate, and severe), producing the Bath Ankylosing Spondy litis Radiology Hip Index ( BASRI-hip or BASRI-h). The system was designed to be specific for AS radiographic change at the hip and includes circumfer ential joint space narrowing, osteophytes, erosions, and protrusio acetabul ae. This score can then be added to the BASRI-spine, forming the grading sy stem BASRI-total, scored 2-16. Radiographs of 134 patients were used to tes t reproducibility. Blinded radiographs of 100 non-AS patients were included randomly to assess disease specificity. Sensitivity to change was determin ed using 438 radiographs from 122 patients, over 219 time intervals. Results. Inter and intraobserver variation for the right and left hip showe d 83-84% and 94-96% complete agreement, respectively. Disease specificity w as 0.76. If non-AS patients with a total hip replacement were excluded, dis ease specificity was 0.83. Sensitivity to change became apparent at one yea r (p < 0.001). Grading the hips using a single radiograph takes seconds. Conclusion. BASRI-h is a reliable method for grading hip radiographic chang e in AS. It is disease-specific, sensitive to change, simple to use, and ra pid to perform.